Ubiquit UMR PPPoE termionation/failover and fallback? :: Home Networking, Internet Connection Sharing, etc.

Here's what I'd like to do but asking before I shell out.

I'd like to use a Ubquiti Mobile router to terminate the PPPoE session (OR FTTP now through CIX/ICUK), with a Three sim in as backup

Does this device have fallback to the wired connection when it recovers or is it just failover?

Can it terminate a PPPoE session.

My intent is to pair it with an HP/Aruba AP-22D to provide wi-fi and also power a PoE DECT base.

I could do with hearing from anyone who is using the UMR in the way I've described above,

Thanks

Virgin (ADSL) => Namesco => Newnet => O2 => Plusnet => Zen => Newnet => Zen => Freeola => Vivaciti (using O2 Wholesale DSL) => Xilo (C&W Wholesale) => Xilo (O2 Wholesale) => Xilo (TT Wholesale due to O2 Wholesale closure) => Zen LLU =>> ZeN FTTP (Openreach 300 Mbps down, 47 Mbps up) => (waiting for) Andrews and Arnold - Openreach 100 Mbps down and 20 up)
Router: Zyxel NR5101

Note: I don't lay turf for anyone. astro or otherwise, all views and opinions expressed are my own based on experience.