Proper diagnosis is important for treatment, only modalities will not help.

Your stiffness due to lack of mobility and degenerative issues. You need to start withjointace DN capsules once daily along with your regular medications and start with basic joint mobility exercises.

X Ray Mri must . Keep continue your physiotherapy treatment.

https://www.youtube.com/watch?v=HxvRQ9ZJ8vQ Chiropractic Mobilization will help. Avoid bending in front. Postural Correction- Sit Tall, Walk Tall. Extension Exercises x 15 times x twice daily. Apply Hot Fomentation twice daily.

It's a good sign that your pain has reduced...now slowly progress to the exercise program prescribed by your physiotherapist..that will relieve your stiffness....it took some time but you will feel better soon

It actually depends on what is the conidition you have! Well its actually a good sign.! I think you tell this to your physiotherapist! He may progress to next step that is stretching which may relieve your stiffness(in case u have tightness) Please do infrom about this to ur physiotherapist.

Yes as stated previously research evidence for electrotherapy alone is limited. If used in conjunction with other treatment it is ok. You should have a course of mobilization, strengthening and stretching exercises and Tens could be re tried when stiffness has reduced with exercises.

SWD and Tens will never treat the cause. Identifying the structure causing the pain is vital. Is it disc or nerve or joint or muscles etc. If you have more stiffness in the morning and after long sitting hours, then it's likely to be disc. Quickly address it before it gets Chronic. MRI might help to know more.