Is it possible to use pagekite or ngrok on glitch?
Yes, but why would you need it? Ngrok is for opening either a TCP or HTTP tunnel to the public Ngrok servers, suitable for people who don’t have access to port-forwarding. With glitch port 3000 is exposed as .glitch.me:<80|443>
You don’t actually have to create a web-server with Glitch, you could open a minecraft server, or a TCP socket server.
Do you have any specific usage for Ngrok or Pagekite. What do you want to achieve? It might (or most likely) is possible without them.
You can actually only expose HTTP servers with glitch. Ngrok et al. is needed for TCP.
Yes you can use them.
Actually, this is not technically correct. The server (container) exposes its ports, what you’re thinking of is whether or not the client can reach it (hence the reverse-proxy). As long as the TCP connection opens following the HTTP(S) connecting spec it can still actually connect to a TCP server tunneled through HTTP (tunneling a TCP connection through the reverse-proxy).