Topic: My ISP gave me a router with OpenWRT: can I extract the firmware?

So that it can be flashable on all Technicolor TG789vac v2?

My ISP modified OpenWRT and put it on its routers. The router can read and flash third party firmware reading them from a tftp server.

My question is: is it possible to create a re-snapshable firmware file of the stock (OpenWRT 99%) one?

I googled, but this is a delicate question, so I thought it would be better to ask here.

Thanks in advance!

p.s. I have root access via SSH.

BusyBox v1.23.2 (2017-03-09 02:08:29 UTC) built-in shell (ash)

 ______   __     ______     ______     ______     __         __
/\__  _\ /\ \   /\  ___\   /\  ___\   /\  __ \   /\ \       /\ \
\/_/\ \/ \ \ \  \ \___  \  \ \ \____  \ \  __ \  \ \ \____  \ \ \
   \ \_\  \ \_\  \/\_____\  \ \_____\  \ \_\ \_\  \ \_____\  \ \_\
    \/_/   \/_/   \/_____/   \/_____/   \/_/\/_/   \/_____/   \/_/

                N E X T   G E N E R A T I O N   G A T E W A Y

 NG GATEWAY SIGNATURE DRINK
 --------------------------------------------------------------------
  * 1 oz Vodka          Pour all ingredients into mixing
  * 1 oz Triple Sec     tin with ice, strain into glass.
  * 1 oz Orange juice
 --------------------------------------------------------------------

Product: vant-6
Release: Aqua (16.3)
Version: 16.3.7636-2921002-20170419153951-718b590506a915e24be58946f4755c0c617d9c8d


Hash config:         718b590506a915e24be58946f4755c0c617d9c8d
Hash openwrt:        6c42ccd019341602a510e4984926f77957cec937
Hash kernel:         0fbe1548eadea50c295b8b839aee7a52668c8325
Hash packages:       0f8aa1264d7a3bf6e4304f0f8ddfdabc4ddac7e4
Hash technicolor:    12432aba3b37fe3a9fda3bd9cc4e8da3fa5fbb40
Hash routing:        7b853f235ce96cd14f3abaebf9253c5ca7f72f7d
Hash lte:            91e34310893a4c4e7a9093cd3866924c285deb6b
Hash custo:          27310c4b16dc4c0fbdfc8d2591680dc10a609083
Hash mindspeed:      91b6a7a4d703268d6023c3a58da3d33fc62e7ed8

Bootloader: 2.0.85