5 Connection questions

[Linc L]

Hello there,

I set up an openconnect vpn server with the anyconnect client. It
worked fine for quite a while until someday I can't open any web or
ping any IP suddenly without changing any configuration. In the
weirshark, I saw a message that never seen before: from my IP to the
server IP the QUIC packet public reset. Usually in weirshark the QUIC
packet works fine. I can't use the vpn anymore from this day.

Yesterday I redeployed the vps server and closed all updates function
of the anyconnect client, also rewrote firewall rules of the server,
then the VPN connection is back to normal. At first I can see lots of
quic packets then the QUIC public reset message appears again. The
strang thing is I still can open the webiste the ping IP. In the
weirshark, there are TCP and TLSV1.2 there, instead of QUIC.

A reference: There's a GREATFIREWALL just in the middle of the server
and my laptop.

My questions are:

1,It's a randomly choice of protocols? QUIC or TLSV1.2? Can I manually
configure it?

2,Why I get a QUIC public reset packet? The router sent it? The
GREATFIREWALL send it? Or the server send it?

3,Why I can't ping my server as soon as I get the VPN connection?
Meanwhile, I can ping other websites?

4, What should I do next to enhance the safe connection?

5, I'd like to know if the ISP or others can block protocols? At which
level? Just for my account? My IP? Or others?

Thank you in advance!