Various masaail of Jamaat Salaah and Imaamat

Q: In a Shafie masjid, when the imam makes salams at the end of the prayer, the congregation waits until he has completed both salams, then they make their own salams. Sometimes the salams of the imam are lengthy, making the congregation wait for a long period (longer than 3 subhanallahs). If a Hanafi follower also delays his salam in this manner (waiting for the imam to complete), will his salat become invalid due to delaying a wajib (i.e. intentionally delaying the first salam)?

Q: Is it preferable for the Imam to lengthen the Ruku' briefly when hearing someone entering the Masjid to join the Salaah?

Q: My question is that we read the Alhamdu shareef in our namaz. When we read namaz in jamaat then do we need to read the Alhamudu shareef or not? 

س: لو شك المأموم في الركعة الثانية أنه قرأ الفاتحة في الركعة الاولي ام لا,ماذا يفعل؟

Q: If one wants to pray a Fardh Salah in Jamaat, can one join a person who is praying a Sunnah Salah? What if one joins a person who is praying a Sunnah salah, but you mistakenly assumed that he is praying a Fardh?

Q: When reading salaah behind an imam, what does one read in the standing position (does the person following read surah fatiha and a surah)?

Q: When should the muqtadi start to change posture in salat (e.g. from qiyam to sajdah): should he start moving immediately when the imam starts saying "Allahu akbar" or should he wait until the imam has completed saying the whole phrase "Allahu akbar"? Or should he, if he can see the imam, wait until the imam has totally completed his change of posture.

Q: If the Imaam breaks his wudhu during leading prayer, I know he can appoint another to be imaam, but is it also aloud that the jamaat does continue each individually their salaah ? Also, if the imaam is just leading 1 person, what is the situation then?

Q: I went to a musjid late, when asr namaaz was over. However, I noticed a second jamaat taking place in the sehen,so I joined it. I got the last rakaat. So after salaam I completed my 3 rakaats. Now, after a few days, I discovered that the jamaat namaaz which took place was by musaafirs, so they read 2 rakaats, and I completed 3 rakaats, what is the condition of my namaaz? 

Q: It takes our imam a bit long to go into sajdah, standing up from sajdah, etc. So what happens, for example, is that after qaumah, as the Imam goes down into sajdah, he says Allahu Akbar, and we also go into sajdah, but some of us reach sajdah before him. Is his and our salaah valid? Should we request him to rather try and do his postures slightly faster? I think it is because of his weight problem.