So i know this is old crapy device, but i have it laing arroud for like year and i dont have any use for it, it is isp brandet but the interface is the same it runs some kind of linux in the backend
Services: ssh, telnet, ftp, http
The web ui: https://setuprouter.com/router/comtrend/ct-5367/screenshots.htm
My question is, is it recomndet to install openwrt?
I will use it just as a smart switch so i can untag certen ports of the bulit in switch and pass vlan trafic to the physical port for devices that dosent support vlan tagging
Also is the built in switch capable of suporting at least 100mb network 
Nope, this device is too old and resource limited. It cannot run a current version of OpenWrt, so it is entirely unsupported.
Im Well aware of that but with the stock firmware this thing is usless
Is it posible to install old version of openwrt just to be able to use the managed switch i dont need it to be router i just want to use it like a "smart" switch?
Sure... I guess you could install OpenWrt and use it as a managed switch.
Okay but the next question is how to install it becuse if i try from the web panel the router says "iligeal update"
And i cant find if this thing has tftp recovery, i managed to login to the device shell and i see a tftp binary but the shell dosent have upgrade command
Did you follow the instructions:
The router dosent go in to any kind of recovery, i pressed and hold it for 20s but the device only factory resets, if i login to the router dashboard it is an iligeal update
Did you set a static IP on your computer (via ethernet)?
Ofcorse, but without result
this is what i get on the stock firmware shell
ADSL Router Model CT-5367 Sw.Ver. C01_R08
Login: root
Password:
> help
?
help
logout
exit
quit
reboot
adsl
xdslctl
xtm
brctl
cat
loglevel
logdest
virtualserver
ddns
df
dumpcfg
dumpmdm
meminfo
psp
kill
dnsproxy
syslog
echo
ifconfig
ping
ps
pwd
sntp
sysinfo
tftp
wlan
arp
defaultgateway
dhcpserver
dns
lan
lanhosts
passwd
ppp
restoredefault
route
save
swversion
exitOnIdle
wan
build
version
nat
ipfilters
acccntr