Yes, the Sagrada Família adult ticket on the basic ticket page costs €26 for sightseeing. The €26 ticket includes the Basilica and museum, with the audioguide app. Mass is for worship. You need a separate booking to tour the church.
In October, the Basilica opens 9:00–19:00 Monday to Friday, 9:00–18:00 on Saturday and 10:30–19:00 on Sunday. The Basilica's opening-hours page says special events can change these times. Your ticket is valid only for the time you booked.
The Basilica's FAQ puts ticket sales at roughly two months before your visit, through the official site or app. Bring the photo ID that matches the name on your ticket. You cannot enter late. Once you leave the grounds, you cannot go back in.
Your ticket: Sagrada Família, €26 per adult, with the Basilica and museum plus the audioguide app.
Plan around: a separate sightseeing slot if you want to see the museum as well as go to Mass.