Explanation
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: MPLS and VPN Architectures Book, Volume 1
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
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... A stratum server may also peer with other stratum servers at the same level to provide more stable and robust time for all devices in the peer group (for example a stratum 2 server can peer with other stratum 2 servers).
NTP uses the concept of a stratum to describe how many NTP hops away a
machine is from an authoritative time source. A stratum 1 time server
typically has an authoritative time source (such as a radio or atomic clock, or a Global Positioning System (GPS) time source) directly attached, a stratum 2 time server receives its time via NTP from a stratum 1 time server, and so on.
Reference: https://www.cisco.com/c/en/us/td/docs/routers/asr920/con
figuration/guide/bsm/16-6-1/b-bsm-xe-16-6-1-asr920/bsm-timecalendar-
set.html

Explanation
Traffic shaping retains excess packets in a queue and then schedules the excess for later transmission over increments of time. The result of traffic shaping is a smoothed packet output rate.