Older devices can connect without becoming Wi-Fi 7 devices
A backwards-compatible Wi-Fi 7 router can serve Wi-Fi 6, Wi-Fi 5, and older clients on supported bands. Those clients retain their own radio, stream, channel-width, and security limits.
Check the client specification, not only the phone or laptop year
Look up the exact wireless adapter or device model for 802.11be, 6GHz, supported channel width, stream count, and MLO. Two products sold in the same year can have very different radios.
MLO requires support at both ends
Multi-Link Operation is a Wi-Fi 7 feature, but the router and client must both support compatible modes and current software. A Wi-Fi 6E client using 6GHz does not automatically gain MLO.
6GHz range and eligibility differ from 2.4GHz
The 6GHz band offers additional clean spectrum but generally has a shorter usable range through obstacles. Regulatory region, supported security, device capability, and placement all affect whether a client can use it.
Verify the wired side of the upgrade
A gigabit modem port, switch, USB adapter, or desktop NIC can limit a Wi-Fi 7 system. Map WAN, backhaul, and client ports before paying for wireless capacity the rest of the network cannot deliver.
Upgrade for a measured reason
Wi-Fi 7 is easier to justify for multi-gig internet, congested homes, new 6GHz clients, or a planned wired backhaul. Better router placement or one Ethernet run may help more when the current problem is a single weak room.