Yes. You will need whole breast irradiation or accelerated partial breast irradiation (APBI) depending on how big your tumor is in the breast, grade, type of tumor, and any positive axillary nodes. If you have only a lumpectomy, the tumor will come back in the breast by more than 50%.

Yes if you are younger than 70 definitely! Maybe after 70 if node-negative and ER+ her2 -.

The majority of patients require radiation treatment to the breast after a lumpectomy. The only exceptions would be very old or sick patients.

Sometimes controversial. Older patients may reasonably opt out for post-operative radiation and some patients with DCIS(in situ) have been observed without radiation depending on several factors in the past, but my bias is to treat these patients depending on the clinical situation. There is a higher local recurrence rate without radiation, but improved overall survival has often not been demonstrated.

Sometimes, it depends on original size of tumor and number of positive lymph nodes.