There are several questions here;
Does my store app run on start up = no
The store process runs because I have my store app 'pinned' to the task bar
The act of 'pinning' something to your task bar tells the system to allow a very very small % to be set aside so that that software can boot faster... This is irrelevant with modern systems and "from memory" was a stop gap patch added to Vista or early W7 because they are so much slower than XP and Microsoft had a lot of trouble getting people to migrate away from it.
That guide is for w8 or w8.1 which uses the same (
back ground) store process however 8.1.1 has a different version of store and the steps to disable it by registry edit would need different keys... The original author of the guide correctly warns people to make a backup and there are plenty of later posts pointing out the dangers so its a case of "at your own risk" but I would not have done that.
The difference between 8.1 and 8.1.1 can cause the store app to sometimes lock up (
because the animation at store start was incompatible with some of the default "out dated" graphics drivers) from the task bar and this error has been patched by Microsoft updates... If this sounds like your issue i.e, the store app itself refuses to open from the task bar, then your options are allow Microsoft to update the system to a higher build or (
better) replace the crap drivers with ones direct from the g-cards maker.
I recommend, you press [windows key]+[x] and the [t] to open the task bar... Goto app usage and press the 'delete history' link then
*shutdown the system and reboot it to confirm the store app is in deed running after your preferences changes.
*Note, a system restart is different to a system shutdown in modern systems and offen skimps some of the maintenance.