Bugger it I'm just going to answer
1) The first reason is that there is no S48 notice served, and so the tenant cannot be evicted. In case anyone doesnt know, the S48 notice details the name and address(in England And Wales) of the landlord, and can be contained within the TA. The second slightly more obscure reason is that S21 notices have to be issued unequivocally and without condition. Therefore by stating that it will only be acted upon should the tenants be bad, a condition has been created which therefore invalidates the notice.
2) Notice 2 WOULD be successful, despite the dates, as you can issue a Section 21 with 2 months notice at any time during the fixed term - the date does not have to coincide with the end of a rental period.
3) First of all, notice 4 has superseded and invalidated notice 3. Also, as notice 4 is issued during a SPT, the notice must end at the end of a rental period. Therefore notice 4 is also invalid.
4) Both notices are now invalid. A new notice must be issued to gain possession after the 31st of January, before the end of November.
5) The notice could have been issued "without prejudice", which would not have invalidated notice 3
