How to install frappe and erpnext by version ?

Install per-requirements. https://frappe.github.io/frappe/user/en/bench/guides/manual-setup.html2
Clone bench of v3.x and install bench using 'sudo pip install -e bench-repo'

then run following commands, hope it will helpful

bench init frappe-bench-v6 --frappe-branch v6.x.x bench get-app --branch v6.x.x erpnext https://github.com/frappe/erpnext bench new-site site_name

bench --site site_name install-app erpnext

How to install frappe and erpnext by version ?

Install per-requirements. https://frappe.github.io/frappe/user/en/bench/guides/manual-setup.html2
Clone bench of v3.x and install bench using 'sudo pip install -e bench-repo'

then run following commands, hope it will helpful

bench init frappe-bench-v6 --frappe-branch v6.x.x
bench get-app --branch v6.x.x erpnext https://github.com/frappe/erpnext
bench frappe --install_app erpnext