Confirmed, no charges other than the Rs.50/month. This fee will be deducted from your trading account, not from your MF units.
No deductions when you withdraw the money after 3 years. No exit load, no tax implications as well.
Yes, you can extend your holding period. The lock-in period is 3 years but you can hold for as long as you like.
Yes, the ELSS statement can be downloaded from Coin.