The answers to your first and last questions are both no, but I couldn't tell for sure when it comes to the second. I've always sent my envelopes the same day I recharged whenever i've done the event in the past.

you need at least 11 ppl online (including yourself) to start sending red envelopes, just in case your group isn't that active at certain times.

Hi! Just to clarify. The Anniversary Red Envelope has two parts in coupon rebate. 20% Recharge rebate for yourself (the one who recharged) and 10% Red Envelope Rebate intended for your Group Members. The Red Envelope intended for Group Members cannot be claimed from the person giving the Red Envelopes.

Coupons stay for the duration of the event. However, once coupons are sent, they are valid for 2 hrs, after which they are unclaimable (you can find information below).

You cannot send directly to players, it must be given as a red envelope to group members that are on at the time of sending. This means, anyone that is online has a chance of obtaining the Red Envelope.