Largely its done by language. Exceptions I suppose are UP,MP,Rajasthan etc which all speak Hindi (or very close dialect). Sometimes the language connects to an ethnicity (depending how you define), sometimes not (i.e multi-ethnic group speaking same language...or same ethnic group speaking many languages across diff states).
Yes each state has own state assembly. Some have one house, some have two.
Generally the larger the state, the more (total) legislators it will have. UP I believe has the most (given its largest population state) of more than 500. An average population state like Tamil Nadu has around half that. Small states like Sikkim can have a few dozen like 30, 40 etc.
Yes there can be no conflict with the higher federal authority (essentially the constitution). Any potential conflicting legislation from a state has to be referred to supreme court I believe to ensure compliance....central govt cannot do this automatically (that would be an overreach since they are not a judicial body), they have to get the AG to refer it to supreme court if it does not get referred some other way (say by a citizen) in first place.
Yes there are district level government bodies and also sub-district (Taluk, mandal, tehsil etc, just a naming convention depending on state). Sometimes a metro/municipal area will expand into a number of them (past city proper district etc) so a bunch of them will be subsumed (or be equals) in authority to the metro authorities in various areas. They are administrative in function and have elections governing them as well (say for mayor, legislative councilors etc) where not covered by state legislature appointment.
These differ from voting district (constituency) which are done according to census to try have each as close to same population as possible (each 1 represents 1 seat in the lok sabha, i.e national popular lower house). Sikkim for example has just 1 voting district (in essence the whole state is 1 seat in lok sabha) but 4 administrative districts.
Mostly (and same goes for governors of the states, which are again appointed by the centre as their highest representative in the respective State)s. But the President is the head of state and does have certain significant powers from the constitution....and ranks in de jure authority higher than prime minister.
President is ( afew examples):
- the commander of the armed forces
- can refuse to sign a bill sent to him (effectively a veto, but very very rarely the case, normally it will be re-worded at most) if he feels it violates the constitution of India (this can be the only reason given he is bounded to act on advice of the PM always). The President has the final executive authority one can say.
- is the one that decides who to call to attempt to form govt after a national election (a governor does this for a state). President also appoints all the governors (and can dismiss them)...along with executive officers like AG, CAG, supreme court judges etc.
- Head of state means he has seniority and 1st precedence for visiting foreign leaders/dignitaries and also officially handles all ambassador appointments by other countries