Now it's not easy to say because all limited user never get 2 mbps speed in night but still at least in Kolkata most of the user getting around 2 mbps speed at night(I am also getting that) so Home 500,C,C+ or other limited plan is best for heavy downloading probably UL 1350 also good but obviously it's little high rental plan.
No land line is must but if you apply for combo plan at least no phone rental will be apply then
- Home 500 -- rental 500 Rs + phone rental according to plan free usage 2.5 GB free call according to landline plan
- Home 500C --Rental 500 Rs no phone rental free usage 1.5 GB free calls 175
- Home 500C+ --Rental 600 Rs no phone rental free usage 2.5 GB free calls 50
No guarantee, but still i am getting in kolkata 1.5-2 mbps.I am hoping you also get such speed.
Probably little short of 5 GB better not expect too much just on a average 4-4.5 GB per night(may be it can touch 5 GB sometimes)
Normally there is no risk present (start download 2.05 AM and stop at 7:55 AM for safe) but how can I say that they will never make a mistake if they do so then obviously your bill will be revised but remember may be you have to waste some time for that.
Which plan ?
If your plan is Home 500 C+ then your bill will be 600+ 10% service tax =660 Rs(approx) (without usage and extra calls)
It's all vary according to USB,Ethernet& wifi.Type I has one Ethernet port & USB port Type II 4 ethernet prot Type III & IV have wifi facility.
SO choice according to need.
torrents work in BSNL BB very good just port forward needed for modem(except Nokia-siemens C2110)
Normally it takes 15-20 days to get new connection with password in calcuttatelephones exchange but sometimes exchange have few problem in that case it can take 1-2 month also so before apply BB please go your local exchange and ask that question they will tell you perfectly.
Go exchange and apply the BB connection if local exchange deny to take application then apply in zonal head exchange try to avoid online connection it's did not work in all area.
Which exchange you belongs ?then may i help you .