Hi Sarika,
1&2. Let's start with the definition of Schedule Model first:
Schedule Model - A representation of the plan for executing the project's activities including duration, dependencies, and other planning information, used to produce a project schedule along with other scheduling artifacts. (PMBOK 6, pg 722)
For example, think of the activities you identified and sequenced, along with their durations, in a CPM graph (or a Gantt/Bar graph).
Project Schedule - An output of a schedule model that presents linked activities with planned dates, durations, milestones, and resources(PMBOK 6, pg 717)
Essentially, Project Schedule = Schedule Model + Scheduling Method + Scheduling Tool + Project Information (PMBOK 6, pg 176)
In order to produce a Project Schedule, you must first have a Schedule Model in hand. That is why Project Schedule is an output of the Schedule Model, in this case it is not related to the ITTO context.
3. For most projects, you will encounter many unknowns and changes throughout the cycle. During the Control Schedule process. If changes were made and unknowns were encountered, the TTs are used to make changes to the schedule so that the project performance can realign with the baseline. To answer your question, many of these TTs are the same except they are used in a different time during the project.
Hope this helps,
