#!/bin/bash
s="User's name is adam
Account's name is adam_acc
User's name is adam.eve
Account's name is adam.eve_acc"
sed 's/\<adam\.eve_acc\>/user_4/g; s/\<adam_acc\>/user_3/g; s/\<adam\.eve\>/user_2/g; s/\<adam\>/user_1/g;' <<< "$s"
IyEvYmluL2Jhc2gKcz0iVXNlcidzIG5hbWUgaXMgYWRhbQpBY2NvdW50J3MgbmFtZSBpcyBhZGFtX2FjYwpVc2VyJ3MgbmFtZSBpcyBhZGFtLmV2ZQpBY2NvdW50J3MgbmFtZSBpcyBhZGFtLmV2ZV9hY2MiCnNlZCAncy9cPGFkYW1cLmV2ZV9hY2NcPi91c2VyXzQvZzsgcy9cPGFkYW1fYWNjXD4vdXNlcl8zL2c7IHMvXDxhZGFtXC5ldmVcPi91c2VyXzIvZzsgcy9cPGFkYW1cPi91c2VyXzEvZzsnIDw8PCAiJHMi