Wireless Access

I have a customer who want to have almost all acces points to work without ethernet he want the Uplink to through WIFi ,but I have more than 100 APs I know that we can use mesh but can I make for example 1 AP as mesh portal adn 10 Ap as mesh point ? and also can I use AP-275 for this and from my prespective I can see that this will have cons. so I need the advise what to do ?

If you are doing controller-based deployments, you can put 10 mesh points on a portal (just understand the bandwidth 'costs' and design limitations. If you are using instant, you are more limited (2 hops and up to 8 mesh points).

None of Aruba's 11ac Instant APs can act as 'WiFi Extenders'. You can look at the HP 501 to fill that need if that works for you. 

I need to know should all APs need a clear line of sight? and lets say teh portal fail thats mean the other 10 mehs ponts will fail right?

Generally yes all APs should have line of sight to other APs. 

yes if you only have a single portal and the portal goes down, all mesh points will be down. If you need high availability for your mesh, you should have multiple portals for the same cluster(s).