Fast Roaming Protocols (802.11k, 802.11r, 802.11v) Does Android support the 802.11 specifications that allow fast roaming, i.e. prevent dropouts as you move between access points? If so, on what hardware and in what version?
802.11k assists the device in its search for nearby APs that are available as roaming targets by creating an optimised list of channels. When the signal strength of the current AP weakens, device will scan for target APs from this list.
802.11r authenticates more quickly through Fast Basic Service Set Transition (FT).
802.11v allows the network’s control layer to influence client roaming behaviour by providing it the load information of nearby access points. Device takes this &quot;BSS transition management&quot; information into account when deciding among the possible roam targets.
Apple's iOS does, as documented here and here. Windows 10 does if the WiFi adapter supports it as documented here and here (suspect latter is currently out of date with respect to PSK &amp; open networks).
Some Samsung models do, as documented here.
But I can't find anything on stock Android (Google Pixel).
Each of those amendments you listed above include a collection of methods/mechanisms/features that have been incorporated into the IEEE 802.11 standard to achieve particular goals/improvements. Whether or not these are supported on a device will depend on the following: 


Specific feature/mechanism
Android version
Device vendor implementation and drivers


Also, keep in mind that in order for these features to work, they not only need to be supported on the client device but also supported and enabled at the infrastructure level (e.g. access points). 

Another thing specific to 802.11r (FT) is that it will improve transition times when using 802.1X/EAP (WPA-Enterprise) security. On a preshared key (WPA-Personal) network, the difference will be negligible at best.

Last but not least, even if all those mechanisms are supported and enabled you could still experience roaming issues. That's because a wireless network needs to be designed at Layer 1 (RF) so as to provide for a good roaming experience, among other things.



These could be of help:

Crowdsourced client device 11v support list: https://clients.mikealbano.com/home

More info about WLAN roaming: https://community.ubnt.com/t5/UniFi-Wireless/Wireless-LAN-Roaming-FAQ/m-p/1825118