What firmware to choose for Asus WL-500gP?

Question

ASUS

The task is as follows:
1. there are remote units with 1-3 local PCs
2. for there are Asus wl-500gP routers (do not offer a replacement, we proceed from the given)
3. the task is to organize access to the Internet from the local PC by restricting everything except what is allowed ( 1-5 sites, dropbox, google services). those. prohibit everything except what is required.
4. IPoE-20%, 3G/4G-80% is used as WAN. I would like to organize a failover channel between IPoE and 3G / 4G WANs,
I ask for advice on the firmware of the router in order to implement, first of all, task 3, and then task 4.