Satsanghs are very important as they help us progress faster in sadhana due to intense transmissions and also it develops in us a good deal of patience, tolerance and fraternity.

1. On one day felt pressure on the heart and on another day felt vibrations on the left hand. On another day, the vibrations in the heart region started during the sitting, continued even after the sitting was over.
I do not understand your statement 'pressure on the heart'. To feel vibrations is alright, to feel jerks is alright, to feel rocking is alright; but to feel pressure is unusual. Please check up with your physician. Also see whether you had heavy food before the meditation. Note whether this is due to gas in the stomach.

2. During one satsangh initially I felt very light and calm towards end I felt expansion, during that time I was floating in the sky, white light was felt and somebody was sitting besides it and later I was floating in water.
These relate to the internal feelings that you are moving in unknown terrains. Do not give much importance to them.

3. Some people are feeling the flow during the satsanghs. I don't know what they mean. But I am not why is this?
Comparison with other abhyasis is alright but that should not make us evaluate that we are not as better as the others. The nature of Divinity is justice and every one gets what is due. This is a basic tenet that should always be remembered. Not only in meditation, this attitude develops in us Fortitude and Forbearance in our behaviour. These two attitudes are considered as most important in life by persons of Wisdom.

4. Why am I not feeling the vibrations. Why am I not feeling the Buzz Sound, which I used to feel. Some times I feel it. But not every time.
Feeling of Pranahuti is through many ways. Please do read the chapters on Transmission in the complete works of Dr. K.C.Varadachari Volume I. Also the various experiences of the abhyasis reported as Case studies in the Centenary Volume of Satya Padamu would be a useful study. Do also read the article on Pranahuti in our site.

5. Once I felt that my body is just a cover and there is a vaccum inside my body. Whenever I go for satsanghs I sense the fragrance of sandalwood incense even though there is no such thing around physically.
Fragrance of different varieties are experienced but none of them are our concern. Forget about them. The heart is inside us and that is most important to recognize that as also the various knots and points. Inside the body there is dirt as well as light. Do not think you can forget them by thinking that inside it is all vacuum.

6. While conducting Satsangh I saw Rev. Babuji for 2-3 minutes. Rev. Sir’s remembrance came 3-4 times during the same Satsangh.
Do you mean to say you saw an image of the Master. Was it a full blown picture or a pass port sized one? What we need to have is not these visions but to live in the consciousness of Sri Ramchandraji Maharaj. Please read about this and have better orientation. Form and Name have to be surpassed if spirituality is to be understood.

7. Felt immense force descending from upwards which made me to bend down. I felt this in all the satsanghs
Though the bent posture may arise now and then because of the intensity of flow of Grace, it would be better if you could try and put up a straight posture as far as possible.

8. During one of the satsanghs, closeness with the Divine and the wish to merge in Him was felt all throughout.
The ideas of laya, mergence and similar sounding words are good: but for that purity is the essential requirement apart from considerable yatra. Attend more to cleaning and also practice constant remembrance; remembering Him as purity and love helps a lot.

9. After Satsanghs (Morning Satsanghs especially) felt bliss and calmness which usually lasted for most of the day. But on few days the feeling did not last most of the day.
It is remembrance of the condition that was obtained during meditation that ensures the condition to stay on. Of course this may get disturbed if the circumstances are not conducive for retaining the experience consciously during the day. In any case the lightness that is obtained during meditation continues to work sub consciously.

10. Absorbed mostly with awareness of fleeting thoughts and feeling showers of grace with feeling of gratitude.
During Satsangh we should only keep the sang and not judge the quality of that. The awareness of thoughts during meditations is good and is essential from my point of view. Do not think that a meditation or Satsangh where you do not feel any thoughts is a good one: that is only a numb state. Kindly read the articles on Concentration and Control of Mind to understand the nature of meditation in our system.

11. Usually miscellaneous thoughts pass by with a few moments of blank. After meditation I feel closeness to other brothers and more oriented to the Master.
Feeling fraternity is one aspect of Satsangh. But the real Satsangh is feeling the presence of the Master during and after that period of time.

12. In Satsanghs on most days I feel relatively free of thoughts and collected. I get some thoughts related to anything I might have been doing the same day but mostly I feel quiet. However on some days I find my whole body aching and from within an almost unwillingness to relent and sit. I want to be able to reach the end of Satsangh quickly, so I could get up and go. I don’t know why I feel so on some days.
The reason is cleaning that is getting effected during satsanghs is of a different nature where we are getting woven into a common fabric of spirituality. This pain and restlessness to get out of the satsangh will be a recurrent phenomenon. But we should try to be in the satsangh so that our wavelength conforms to what the Divine wills.

13. Sometimes after satsanghs, it took 5-10 minutes to clear that charged condition.
We need to come out of the condition because we have many things to do; otherwise we feel like being in that state for longer period. This we attend to by remembering the condition during the day as far as possible.

14. During satsanghs feelings of devotion and resignation to the will of Master
There is some difference between  it is alright  and “this is the will of Master which I accept totally. We should not feel resigned to the will of the Master: we should accept willingly all that comes to us with gratitude. This step may be tough but that is our aim.

15. In one satsangh, got a feeling of shrinking in a vast expanse while the outer body contour is expanding at a rapid pace.
Expansion is always an expansion in consciousness and it has nothing to do with body contours. Please note the point carefully and observe your condition. Normally no one of us feel our contours of the body while meditating and that being so the question of expansion of body can not be there. This is an alien thought to our system.

16. Sometimes I feel engulfed. Sometimes I feel so low that we give so much importance to ourselves and take pride in our possessions and do not give importance to God who provided us all these in first place. I feel that we should all take part in divine endeavor of our Rev. Babuji.
It is good that you feel like co operating with the Master and that is a good sign of progress in spiritual life. Self centred thinking should change into other centred first, universe centred next and cosmic centred much later. Keep growing and you will feel oneness with the divine.