can we still use firefox on windows 7?

https://support.mozilla.org/en-US/kb/firefox-users-windows-7-8-and-81-moving-extended-support The old Firefox 115 ESR is based on the old Firefox 115.0 Release but with allowed security and stability fixes since. However the Firefox 115.33.0esr Released today is the last planned updates as there is no more extension in updates. Firefox 116.0 to current including the Fx 140.8.0esr and Fx 148.0 Release requires Windows 10, 11 to run. Chrome/Chromium browsers dropped support for the EOL Windows 7, 8, 8.1 back in early 2023. Another way to run current versions of Firefox on your system is to use a current Linux distro with a light desktop. However if your hardware is old with a 32-bit CPU then you are limited in 32-bit Linux distro options now and 32-bit Linux support was dropped as of Firefox 145.0 and later. As for can you still use the old Firefox ESR then yes. However many websites already prompt people to update their Firefox to use the site for example.