Is it possible to fall from Platinum to Gold and from Gold to Silver on season 5? Since in every season stuff like that change I would like to know. And if yes, how many games you need to lose in a row in order to get demoted?
Yes it is still possible to get demoted if your MMR is at least 1 tier below your current tier. However you wil recieve a warning first about a possible demotion.
Other than that it's obviously also possible to get demoted by the LP decay that's triggered from inactivity.