"I am planing to make a MCU based battery charger"

Please see my earlier post - there are some risks involved here: remember that batteries can contain heavy metals and nasty chemicals, may give off explosive gases, and may themselves explode if mis-treated.

Note that there are already many single-chip battery charger ICs available; eg, Benchmarq (sp?), Maxim.
Many (most? all?) of them probably already contain microcontrollers.

"want to find out about followings"

You need to visit battery manufacturers' websites, and read the specs - they will state the charging requirements for the various types.
Maxim also has some application notes which address this.
Try your favourite internet search engine.

"2. How we can sense that battery is fully charged in constant current and in constant voltage type battery."

Again, read the spec!
For constant-current charging NiCd & NiMH, there is a definite change in the dV/dt curve which marks the charging endpoint.
The change is slightly different between NiCd (it goes negative?) and NiMH (it becomes zero?)

"3, What type of batteries are car batteries. Const. I or Const. V."

Car batteries are lead-acid; charging is usually constant-voltage.
Again, get the spec.

"4, How can we calculate sufficient current required in constant current batteries."

See above for NiCd & NiMH - there is a definite detectable end-of-charge point

"some one suggested the 10% of the max. current rated on the battery will be enough."

That is actually 10% of the rated Ah capacity; eg, a 4Ah NiCd would be charged at 400mA for ~14h.

This is the norm for NiCd domestic "trickle" chargers - it will recharge a battery in ~14hrs, and the battery will not be damaged by being left on this charge rate for too long.

At higher charge rates, it becomes important to actually detect the charging end-point, rather than rely purely on time. This is the case when batteries can explode!

At high rates, it is also important to monitor the battery temperature - and cut the charge if they get too hot!