The installation has not gone passed stage 6 for over 2 hours. i have deleted the contents populated in the database and restarted the whole process. Please help.

1) what forma version are you installing?
2) what environment? Os / PHP version / web server version/mysql versions
3) post your web server error log
4) is step 6 concerning languages? What languages did you select?

I have uninstalled and started again. This time after the installation was completed, I tried removing the install folder and it has been throwing a 404 error
"Not Found
The requested URL was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."

V-3.1.0
Using Cpanel
php 7.4
Apache Version 2.4.53
MySQL Version 10.2.43-MariaDB-log

You're missing something. But I can't help without being on your instance.

Problem
I'm having a similar problem as OP: Hours stuck at "loading" Importing database

Troubleshooting
I initially tried multiple language install. Didn't work, so i created a new database and tried English only install. Same problem.
I checked PhPMyAdmin: In both cases the database seems to be populated OK. 253 tables.

Details
forma v3.1.0
cPanel 106.0.7

Database Server
Server version: 10.3.36-MariaDB - MariaDB Server
Protocol version: 10

Web server
cpsrvd 11.106.0.7
Database client version: libmysql - mysqlnd 7.4.30
PHP version: 7.4.30

My hosting package has restricted access to cPanel features - don't think I can access the web server error log.

It's unlikely you can solve without logs or debug.
You can try upgrading your mysql server, but it's a blind shot.