Here's a comprehensive guide for defeating Tseng and Elena in "Final Fantasy 7 Rebirth," including requirements, a detailed walkthrough, strategies, and additional tips:
Requirements:

Tseng and Elena Boss Guide in Final Fantasy 7 Rebirth
•Location: Fought in the Temple of the Ancients during Chapter 13.
•Rewards: Experience, AP, and progression in the story.
•Party Composition: Aerith, Red XIII, and Yuffie are your characters for this fight in Chapter 13, "Where Angels Fear to Tread."
Materia:
•Ice Materia: Tseng is weak to Ice.
•Lightning Materia: Elena is weak to Lightning.
•Healing Materia: Cure or Pray for Aerith to heal the party.
•Barrier Materia: To reduce damage from their attacks.
•Assess Materia: To learn about their weaknesses and attack patterns.
Gear:
•Equip Aerith with a weapon like the Guard Stick for magic, Red XIII with the Mythril Collar for stagger, and Yuffie with the 4-Point Shuriken for ranged attacks.
•Consider gear with Ice or Lightning resistance or link Elemental Materia with these elements in armor.
•Level: Aim for around level 50-55, but with strategic play, lower levels can work.
Detailed Walkthrough: 
Phase 1: Initial Attacks:

Tseng and Elena Boss Guide in Final Fantasy 7 Rebirth
1.Tseng: Knifehand Swipe, Furor, Vortex Kick, Chi Burst
2.Elena: Grenade Kick, Stun Grenade, Butterfly Kick
3.Strategy:
4.Target Elena First: She's easier to stagger and pressure with Lightning attacks. Use Yuffie's Lightning Ninjutsu and Aerith's Thunder spells.
5.Tseng's Combos: Dodge or block Tseng's combos, specifically aiming to evade the last strike to pressure him.
6.Avoid Grenades: Move or guard against Elena's grenades to prevent being stunned.
Phase 2 (Synergy Attack - Sync Stance):

Tseng and Elena Boss Guide in Final Fantasy 7 Rebirth
1.Combined Attack: They perform a series of dangerous moves together.
2.Strategy:
3.Interrupt: Use strong abilities or spells when they start their Sync Stance. Yuffie's ninjutsu or Aerith's magic can be effective here.
4.Red XIII's Role: Use his speed to attack from behind, focusing on Elena, while others disrupt.
Phase 3 (Post-Sync Stance):

Tseng and Elena Boss Guide in Final Fantasy 7 Rebirth
1.Revival: If Elena is defeated, Tseng can revive her once with a Phoenix Down, but she returns with half health.
2.Strategy:
3.Tseng Focus: Once Elena is down, focus on Tseng with Ice attacks.
4.Limit Breaks: Use these when Tseng is staggered or after he revives Elena for maximum damage.
Strategies: 
Exploit Weaknesses:

Tseng and Elena Boss Guide in Final Fantasy 7 Rebirth
•Tseng: Use Ice spells or abilities like Blizzard or Yuffie's Ice Ninjutsu.
•Elena: Lightning spells or Yuffie's Lightning Ninjutsu and Aerith's Thunder.
•Stagger and Pressure: Pressure Tseng by avoiding the last hit of his combo. For Elena, hit her with two powerful abilities or spells.
•Defensive Play: Use Barrier to lessen the impact of their combined attacks. Red XIII can use his Vengeance Mode for damage reduction.
•Synergy Abilities: Utilize Red XIII and Yuffie's Synergy Abilities to manage the fight's pace; Red can tank while Yuffie attacks.
Tips: 

Tseng and Elena Boss Guide in Final Fantasy 7 Rebirth
•ATB Management: Use Aerith for healing and magic, save ATB for crucial moments like Sync Stance interruptions.
•MP Management: On Hard Mode, link elemental Materia with MP Absorption or use abilities over spells.
•Positioning: Keep moving to avoid Elena's grenades and to position for counterattacks on Tseng's combos.
•Limit Breaks: Save these for when one or both are staggered or when Tseng attempts to revive Elena.
•Hard Mode: Equip Elemental Materia with Ice and Lightning on weapons, use Barrier and Manawall strategically.
•Summoning: If you have a summon, use it when both are staggered or after dealing with Elena for a significant impact on Tseng.
•Yuffie's Versatility: Her ability to switch between elements makes her invaluable here; use her to adapt to the situation.