Because some PE routers might receive routing information they do not require, a basic requirement is to be able to filter the MP-iBGP updates at the ingress to the PE router so that the router does not need to keep this information in memory.
The Automatic Route Filtering feature fulfills this filtering requirement. This feature is available by default on all PE routers, and no additional configuration is necessary to enable it. Its function is to filter automatically VPN-IPv4 routes that contain a route target extended community that does not match any of the PE's configured VRFs. This effectively discards any unwanted VPN-IPv4 routes silently, thus reducing the amount of information that the PE has to store in memory -> Answer 'PE1 will reject the route due to automatic route filtering' is correct.
Reference:
The reason that PE1 dropped the route is there is no "route-target import 999:999" command on PE1 (so we see the "DENIED due to: extended community not supported" in the debug) so we need to type this command to accept this route -> Answer 'After you configure route-target import 999:999 for a VRF on PE1, the route will be accepted' is correct.

Explanation
FlexConnect is a wireless solution for branch office and remote office deployments. It enables customers to configure and control access points in a branch or remote office from the corporate office through a wide area network (WAN) link without deploying a controller in each office.
The FlexConnect access points can switch client data traffic locally and perform client authentication locally when their connection to the controller is lost. When they are connected to the controller, they can also send traffic back to the controller. In the connected mode, the FlexConnect access point can also perform local authentication.
Reference:
https://www.cisco.com/c/en/us/td/docs/wireless/controller/7-2/configuration/guide/cg/cg_flexconnect.html

Explanation
The stratum levels define the distance from the reference clock. A reference clock is a stratum 0 device that is assumed to be accurate and has little or no delay associated with it. Stratum 0 servers cannot be used on the network but they are directly connected to computers which then operate as stratum-1 servers. A stratum 1 time server acts as a primary network time standard.

A stratum 2 server is connected to the stratum 1 server; then a stratum 3 server is connected to the stratum 2 server and so on. A stratum 2 server gets its time via NTP packet requests from a stratum 1 server. A stratum 3 server gets its time via NTP packet requests from a stratum-2 server...

The following different OSPF types are compatible with each other:
+ Broadcast and Non-Broadcast (adjust hello/dead timers)
+ Point-to-Point and Point-to-Multipoint (adjust hello/dead timers)
Broadcast and Non-Broadcast networks elect DR/BDR so they are compatible. Point-topoint/
multipoint do not elect DR/BDR so they are compatible.

Explanation
In this case, we are using your EtherChannel without a negotiation protocol. As a result, if the opposite switch is not also configured for EtherChannel operation on the respective ports, there is a danger of a switching loop.
The EtherChannel Misconfiguration Guard tries to prevent that loop from occuring by disabling all the ports bundled in the EtherChannel.